Conventionally, as a material for forming a microlens, polyhydroxystyrene is known. However, due to the following problems, there is room for improvement. When the polyhydroxystyrene is used as a material for forming a microlens, due to heating performed at a high temperature, the semispherical shape of the microlens changes easily, so it is difficult to form a microlens with a stabilized shape. Moreover, polyhydroxystyrene tends to be easily colored by heating treatment and exhibit deterioration of transparency. Accordingly, coloration is sometimes recognized when the microlens is used.
Incidentally, compounds such as styrene-based polymers, acrylamide-based polymers, acrylic polymers, and vinyl pyrrolidone-based polymers having a boronic acid group on a side chain are known (for example, see Patent Documents 1 to 4). Further, a polymer having a boronic acid group on the terminal has been proposed (see Patent Document 5).
In addition, there is a disclosure regarding the use of a polymer, which has a boronic acid group on the terminal, as a photosensitive resin (see Patent Documents 6 and 7). In Patent Document 6, polyethylene glycol having an average molecular weight of 350 is reacted with a borane-dimethyl sulfide complex to obtain a polymer having a boronic acid group on one terminal. According to this document, 19.4 mol % of the total number of unit structures constituting the polymer contains a boronic acid group.